Seasonal variability of CO 2 air-sea fluxes and DIC in the Southern Pacific Ocean
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Transcript of Seasonal variability of CO 2 air-sea fluxes and DIC in the Southern Pacific Ocean
Seasonal variability of CO2 air-sea fluxes and DICin the Southern Pacific Ocean
Leticia Barbero, Jacqueline Boutin, Liliane Merlivat
4th CarboOcean meeting, Dourdan, France8-12 December 2008
Buoy and ship trajectories in the Southern Pacific Ocean
CARIOCA 01110 April/2004-April/2005CARIOCA 03740 April/2004-June/2005Palmer US Ships April-May/2004 March/2005 September/2005 September/2006
STF
SAF
SAZ
•STF: Climatoligical (Orsi)•SAF: Altimetry data (J.B. Sallée)
Buoy trajectories colour-coded for month
STF
SAF
Palmer Ships: April-May/2004 March/2005 September/2005 September/2006
SAZ
fCO2 (µatm) measured by CARIOCA and ships
AT computed from SST,SSS (Lee et al., 2006)DIC computed from fCO2 and AT (Mehrbach et al. (1973) after Dickson and Millero (1987) )
• ARGO floats co-located in time and space used to compute mixed layer depth (MLD)
DIC (µmol/kg) computed along trajectories
220 data points (0.5% of total)No data for November
Late winter: deep MLD, rich DIC values
In order to increase data: Dong et al. (2008) MLD climatology for Southern Ocean
100% 46000 data points
Deep MLD-rich DIC
Buoy and ship DIC data vs. Dong et al.’s (2008) climatological MLD (m)
Sep.
Oct.
Aug.
Jan.
DIC hyperbolic f(MLD) σ = 19 µmol/kg
DIC = a + b*MLD + c*SST σ = 9.7 µmol/kg
Similar algorithm for fCO2:
fCO2 = a’ + b’*MLD + c’*SST σ = 16 µatm
For |MLD| > 100m: fCO2 = a’’ + b’’*MLD + c’’*SST σ = 8 µatm
August 2005
Dong et al. (2008),Density difference criteria,Δρ = 0.03 kg m-3
MLD (m)
SST (ºC)
SST, WOA 2005 :Objective analyzed mean
Estimation results for August 2005ΔpCO2Exchange coefficient, Kw (Sweeney et al., 2007)
0.04 0.08 0.12µatm
Sea-air flux
(mmol m-2 d-
1)
Mol m-2 yr-1 µatmWeekly Quickscat winds from Ifremer
Takahashi et al. (2009)
Air-sea CO2 flux for August 2005Our study
Flux estimates (Pg C/year), Kw Sweeney et al., 2007:
•McNeil et al. (2007), 40-50ºS: 0.92•Takahashi et al. (2009), Pacific Oc., 14-50ºS: 0.4•Boutin et al. (2008), SAZ: 0.67•This study, SAZ Pacific Oc (72% of total): 0.81
ΔpCO2Exchange coefficient, Kw (Sweeney et al., 2007)
0.04 0.08 0.12µatmMol m-2 yr-1 µatm
(mmol m-2 d-
1)
Estimation of biological production
DIC and AT vs. time DIC and SST vs. time
Aug.
Jan.
Sunrise
Sunset
Time # Days NCP(µmol/kgd)
Chl-a(mg m-3)
30/11-1/12 2 0.48 ± 0.53 0.27
16-20/12 3 1.22 ± 0.59 0.31
18-21/1 3 0.49 ± 0.66 0.14
29-30/1 2 1.17 ± 0.25 0.14
Method described in detail by Merlivat et al. (2008)
hF
tCNCP
1
Net Community Production:
F = air-sea fluxh = MLD
No direct relationship between satellite Chl-a and NCP
Chl-a from MODISA-SEAWIFS weekly average
Estimates of air-sea CO2 flux in SAZ in the Pacific Ocean: 0.81 Pg C yr-1.
Lack of buoy and ship data in big area on the North-eastern Pacific SAZ.
Large variability in DIC during the summer months estimates of NCP (0.5-1.22 µmol kg-1 day-1). Questions remain concerning how representative these values are. Is this an intermittent event or can we extract a mean value?
No direct correlation between NCP and satellite products for low chlorophyll-a concentrations.
Still a work in progress!
In summary:
THANK YOUFOR YOUR ATTENTION
Time # DaysCM-Cm
(µmol/kg)ΔC/Δt
(µmol/kg) q pFair-sea
(mmol/m2d)
h(m)
NCP(µmol/kgd)
NCPint(mmol/
m2d)
Chl-a(mg m-3)
30/11-1/12 2 2.79 ± 0.78 0.52 ± 0.54 0.66 0.63 -2.17 50 0.48 ± 0.53 23.81 0.27
16-20/12 3 3.83 ± 0.50 1.29 ± 0.61 0.68 0.58 -4.34 60 1.22 ± 0.59 73.37 0.31
18-21/1 3 2.21 ± 0.59 0.63 ± 0.65 0.64 0.61 -6.48 45 0.49 ± 0.66 22.07 0.14
29-30/1 2 4.03 ± 0.92 1.34 ± 0.33 0.63 0.61 -7.71 45 1.17 ± 0.25 52.69 0.14